Luminescent reconnaissance slate



June 27, 1961 M. M. GOLDSTEIN LUMINESCENT RECONNAISSANCE SLATE Filed Oct. 20, 1959 Fig.

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INVENTOR. Alfl V/NM GOADSIHA/ BY /i 12 24.. ATTORNEY United States Patent G 2,990,308 LUMINESCENT RECONNAISSANCE SLATE Melvin M. Goldstein, Bronx, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Oct. 20, 1959, Ser. No. 847,669 3 Claims. (Cl. 154-79) This invention relates to a reconnaissance slate so constructed that it may be readily scribed upon and read in darkness or underwater, without chancing that stray illumination will reveal the presence of the person using the slate.

A broad object of this invention is to provide a slate for reconnaissance personnel which may be used in total darkness or underwater wherein items of intelligence may be readily entered thereupon and subsequently read therefrom without revealing the presence of the party using the slate through stray illumination.

Another object of the invention is to provide a slate for reconnaissance personnel which may be used for applying intelligence to either face in total darkness or underwater.

A further and more specific object of the invention is to provide a slate for use by reconnaissance personnel wherein a novel, pressure-sensitive masking film composition is removably applied onto the slate.

Other objects and advantages will appear upon reading the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectional view of the assembled slate structure.

FIGS. 2 and 3 are views of separate portions of FIG. 1.

Referring to FIG. 1, the numerals -10 designate a pair of generally identical transparent sheets or supports, preferably of Plexiglas, the inner surfaces having incorporated thereon, or are otherwise treated with, an adherent layer 12-12 of a light-emitting agent or photoluminescent composition which may be applied in the form of an adherent paint. The material of the lightemitting layers 12-12 can include phosphors incorporating sulfides of zinc, calcium or strontium, so that the layers will be able to emit light with photoluminescent brightness upwardly of 17 microlamberts for many hours, after a short exposure to direct sunlight or an ultra violet light. The sheets 10-10 are cemented together with the light-emitting layers 12-12 disposed interiorly, as shown, by any suitable type epoxy resin 14 which hardens or indurates at room or slightly elevated temperatures when mixed with a hardener. An epoxy resin such as Hysol 2040, a product of Houghton Laboratories Co., Olean, New York, when mixed with an amine type hardener, has been found suitable for this purpose and permits intelligence to be applied to both faces of the slate.

Masking film layers 16-16 are illustrated in contact with the outer surfaces of the transparent sheets 10-10, and this is the case when the slate is ready for use. The numerals 18-18 designate polyester backing sheets, such as Mylar, a product of E. I. du Pont de Nemours & Co., Wilmington, Delaware.

In FIGS. 2 and 3, the assembly of FIG. 1 is shown separated into two sections for the purpose of explaining a preferred method of assembling the slate.

The masking film 16 will first be sprayed or brushed onto the Mylar backing sheet 18, the latter having a preferred thickness of approximately 0.001 inch. The masking film 16 is allowed to dry on the backing sheet 18, as shown in FIG. 3, and the entire assembly of FIG. 3 will 2,990,308 Patented June 27, 1961 then be pressed onto the transparent sheet 10 of FIG. 2, the masking film 16 contacting the transparent sheet 10. It should be understood, of course, that the slate may be assembled as illustrated in FIG. 1, to permit intelligence to be applied to both faces thereof.

Heretofore, in reconnaissance slates and the like, the opaque masking films which rendered the fluorescent or light-emitting surfaces non-visible were tacky, or required excessive pressure on the scriber by the person using it, or were not sufiiciently resistant to tearing and/or distortion.

It has been found that a durable, resilient, pressuresensitive, removable, water-insoluble masking compound, suitable for spraying, can be made from the following compositions, and are set forth by way of illustration and not of limitation:

Grams Carbon black 5 XC-269 Adhesive Xylene XC-269 Adhesive is a non-tacky, viscous, pressuresensitive silicone manufactured by the Dow Corning Corporation, Midland, Michigan. Less or no xylene will be necessary if the masking film composition is to be brushed onto the Mylar backing sheets.

The XC-269 Adhesive was first mixed with the xylene. When the ingredients were thoroughly blended the carbon black, for example, oil-free lampblack, was added with continued stirring, until a smooth lump-free mixture was obtained. The mixture was then sprayed or brushed onto the Mylar sheets, the xylene being suitably evaporated. The masking films with Mylar backing sheets afiixed thereto may now be put away for future use or applied to the Plexiglas sheets, as described hereinabove. If desired, clamps o-r straps may suitably be affixed to the slate for underwater use.

It should be understood that the foregoing disclosure relates to only a single embodiment and composition of the slate construction and masking film respectively, and that modifications to either or both may be made thereto without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A slate structure comprising a base sheet of transparent and relatively rigid plastic material, a layer of photo-luminescent material on one face of said sheet and a water-insoluble masking film formed from a mixture of carbon black and a pressure-sensitive silicone adhesive on the other face of said sheet and said masking film being readily scribed to permit light emission from the photo-luminescent material to visually indicate scribed markings when the slate is used in darkness.

2. A slate structure comprising a base sheet of transparent and relatively rigid plastic material, a layer of photo-luminescent material on one face of said sheet and a water-insoluble masking film formed from a mixture comprising 5 parts of carbon black and 100 parts of a pressure-sensitive silicone adhesive on the other face of said sheet and said masking film being readily scribed to permit light emission from the photo-luminescent material to visually indicate scribed markings when the slate is used in darkness.

3. A method of forming a slate structure for use in darkness which comprises the steps of applying a layer of photo-luminescent material directly to one face of a transparent first sheet, applying a mixture comprising 5 parts of carbon black, 100 parts of a pressure-sensitive l 2,990,308 3 4 silicone adhesive and 150 parts of solvent to one face of References Cited in the file of this patent a plastic second sheet, allowing the mixture to dry on the second sheet to provide an opaque adherent film which UNITED STATES PATENTS is removable thereirom, and then assembling the second 2,387,512 Hilberg Oct. 23, 1945 sheet and adherent film -as a unit to the other face of the 5 2,568,384 Cheronis Sept. 18, 1951 transparent sheet by applying the adherent film directly 2,719,333 V n nt 1955 thereto by' pressure. 7 2,933,602 Gillson Apr. 19, 1960 

1. A SLATE STRUCTURE COMPRISING A BASE SHEET OF TRANSPARENT AND RELATIVELY RIGID PLASTIC MATERIAL, A LAYER OF PHOTO-LUMINESCENT MATERIAL ON ONE FACE OF SAID SHEET AND A WATER-INSOLUBLE MASKING FILM FORMED FROM A MIXTURE OF CARBON BLACK AND A PRESSURE-SENSITIVE SILICONE ADHESIVE 